The current analysis examines the thermofluid properties of an infrared suppression (IRS) system with louvered conical diathermic funnel walls in the presence of surface radiation. An IRS device's flow and heat transfer characteristics are challenging because cold atmospheric air is entrained through the interfunnel openings into the IRS and mixes hot exhaust gas from the turbine in naval/cargo ships. The full Navier–Stokes equation is solved along with the energy equation and radiative transfer equation (where applicable) for modeling a three-dimensional actual-scale IRS device with louvered conical funnel walls. This study elucidates the influence of the Reynolds number ( to ) nozzle overlapping, inclination angle, funnel overlapping, and guide vanes on the air intake and system exit temperature. The calculation of the lock-on range on the ship with or without the IRS device. The performance of a diathermic wall with surface radiation is significantly improved.